For carrying out gene-therapeutic measures it is important to have vectors which can introduce foreign genes into the genomes of cells and which are not toxic for them. An example of such vectors are adeno-associated viruses (AAVs).
AAVs are single-stranded DNA viruses belonging to the parvovirus family. AAVs need helper viruses, particularly adenoviruses or herpesviruses, for their replication. In the absence of helper viruses, AAVs integrate into the host cell genome, particularly at a specific site of chromosome 19.
The genome of AAVs is linear and has a length of about 4680 nucleotides. It comprises two reading frames which code for a structural gene and a non-structural gene. The structural gene is referred to as cap gene. It is controlled by the P40 promoter and codes for three capsid proteins. The non-structural gene is referred to as rep gene and codes for the Rep proteins, Rep 78, Rep 68, Rep 52 and Rep 40. The two former proteins are expressed under the control of the P5 promoter while the expression of Rep 52 and Rep 40 is controlled by the P19 promoter. The functions of the Rep proteins are represented inter alia by the control of the replication and transcription of the AAV genome.
However, the production of AAVs is extremely problematic. In particular, it is difficult to prepare great amounts of recombinant AAVs (rAAVs), i.e., AAVs containing a foreign DNA. Even the attempt of using adenoviruses as vectors for rAAVs does not yield satisfactory results.
Therefore, it is the object of the present invention to provide a product by which rAAVs can be provided in great amounts.